Master
Sergeant Bill Putnam, U.S. Army
conducted a world wide search starting
in 2002, to find a high capacity
magazine that could be used for a .45
ACP conversion on an AR15 rifle that
would also fit the narrow mag well on
the AR15. Only three magazines were
found that were .45 ACP and high
capacity. The Thompson SMG, the
Reising SMG, and the M3 grease Gun SMG.
All from WWII. None of them would fit
the AR15 mag well without major
modifications to the magazines.

In 2004, while serving in Operation
Iraqi Freedom, MSG Putnam had an
epiphany. Why not make a new lower
receiver that used one of the existing
high capacity .45 mags. The first
thought was to use the Thompson SMG
mag since there were millions of them
available and they were very
inexpensive. Problems arose
quickly in the R&D stage. The
upper receiver and bolt carrier would
have to be modified to make it work.
R&D continues today on the
Thompson mag option though it will be
more expensive to produce.

Next MSG Putnam tried the Reising mag.
A successful prototype was made using
a regular AR lower by squeezing the
mag slightly. The main issue with
Reising mags is the price. Original
only held 20 rds and they were around
$100 a piece. 30rd Reising mags were
made by Ken Christie but these still
ran $85. Last was the M3 Grease
Gun mag. The single feed mag worked
best with an Olympic Arms .45 upper
receiver. Olympic Arms is still the
only factory making this caliber
conversion.

MSG Putnam also conceived the
removable carry handle with A1 sights
vs. the standard A2 rear sight while
stationed in Macedonia in 2002. He
contacted Justin Halford of CNC
Gunsmithing www.cncguns.com after
seeing Justin's personal projects
on AR15.com. After Justin made a short
run of high quality A1 carry handles,
MSG Putnam decided to contacted Justin
again to see if it would be possible
to make a dedicated .45 ACP lower
receiver designed to mate with the
Olympic Arms .45 upper, while using
grease gun mags.

Problems were encountered with how to
make a magazine catch that
worked. Justin deserves the
credit for the successful
design and
creation of an unique magazine release that
allowed the use of unmodified
grease gun magazines. The new
magazine release also preserves the
original AR15 manual of arms, by having
the magazine release button in the
same location as the standard AR15,
unlike other conversions on the market
where they use an awkward lever on the
bottom of the receiver. By
preserving the manual of arms, there's
nothing new to learn for the
shooter. These features made
the conversion even better as no
additional modifications needed to be
made to the magazines. Justin
made a few personal conceptual
prototypes to testthe
new magazine release. After
successful testing, the AR45 was born.